1. Field of the Invention
The present invention generally relates to computer facilitated viewing of large images and more specifically relates to computer facilitated viewing of virtual microscope slides.
2. Related Art
In the growing field virtual microscopy, the first challenges to be overcome were related to the digital imaging of microscope slides (“scanning”). Conventional image tiling is one approach that is widely prevalent in the virtual microscopy industry. The image tiling approach to scanning microscope slides employs a fixed area charge coupled device (“CCD”) camera and takes hundreds or thousands of individual pictures (“image tiles”) of adjacent areas of the microscope slide. These image tiles are stored in a computer and an index is used to identify the name of each image tile and its relative location in the macro image. A conventional image tiling approach is described in U.S. Pat. No. 6,101,265. Although slow and cumbersome, conventional image tiling solutions did succeed in scanning microscope slides to create a virtual slide.
Once the virtual slide was present in a computer system, the viewing of portions of the slide was relatively straight forward based on the inherent nature of the thousands of image tiles. If a user wanted to view a portion of a virtual slide, all the user had to do was select the portion and then the system could identify the corresponding individual image tiles and display those tiles. Accordingly, the viewing aspect of virtual microscopy was not very challenging for conventional image tiling solutions.
In particular, a new linear array based line scanning solution has been developed by Aperio Technologies, Inc. This solution employs a linear-array detector in conjunction with specialized optics, as described in U.S. Pat. No. 6,711,283 entitled “Fully Automatic Rapid Microscope Slide Scanner,” which is currently being marketed under the name ScanScope®.
More recently, significantly improved systems for creating virtual slides have been introduced into the virtual microscopy industry. Aperio Technologies, Inc. now provides a linear array based line scanning solution as described in U.S. Pat. No. 6,711,283. The revolutionary line scanning solution reduces the time to create a virtual slide from hours to minutes. In addition to rapid data capture, line scanning benefits from several advantages that ensure consistently superior imagery data. First, focus of the linear array can be adjusted from one scan line to the next, in contrast to image tiling systems that are inherently limited to a single focal plane for an entire image tile. Second, because the linear array sensor in a line scanning system is one-dimensional, there are no optical aberrations along the scanning axis. In an image tiling system, the optical aberrations are circularly symmetric about the center of the image tile. Third, the linear array sensor has a complete (100%) fill factor, providing full pixel resolution (8 bits per color channel), unlike color CCD cameras that lose spatial resolution because color values from non-adjacent pixels must be interpolated (e.g., using a Bayer Mask).
Another significant improvement provided by the line scanning solution is that a virtual slide is contained in a single image file on the computer system, in stark contrast to the thousands of individual image tiles created by a conventional image tiling system. Managing a single image file for a virtual slide requires significantly less operating system overhead than the management of thousands of individual image tiles and the corresponding index. However, the creation of a single image file for a virtual slide, while much more efficient and less time consuming, creates new challenges for the viewing of these virtual slides. A virtual slide file created by a line scanner can be up to 4 gigabytes (“GB”) in size as opposed to the 1 MB size for an image tile.
Therefore, introduction of the superior line scanning system for creating virtual slides has created a need in the industry for virtual slide viewing systems and methods that meet the unique needs imposed by the new technology.